1. Field of the Invention: The invention relates to a gas laser having a gas-filled tube hermetically sealed at least at one of the two ends thereof by a plate-shaped window, which may be inclined at the Brewster angle, the tube being formed of a first material with a thermal coefficient of expansion H.sub.1 at least at its end facing the window, and the window being formed of a second material with a thermal coefficient of expansion H.sub.2, at least on the side or inside thereof facing the end of the carrier, and the two materials being unmatched to each other (.DELTA.H=.vertline.H.sub.1 -H.sub.2 .vertline.&gt;10.times.10.sup.-7 o K.sup.-1). Such a laser structure is known from U.S. Pat. No. 4,063,803.
2. Description of the Related Art:
In many cases, the use of material for the laser tube and its optical terminations or ends having thermal coefficients of expansion which greatly differ from each other, cannot be avoided. Thus, Brewster windows are usually of quartz because this material is intrinsically highly transparent, absorbs practically no impurities even after extended operation and can, in addition, be smoothed without too much effort. On the other hand, certain kinds of glass which are easier to process and above all, are heliumtight as well, are preferred for the tube jacket or the capillary. These types of glass have a thermal coefficient of expansion which is in general between 35.times.10.sup.-7 degrees K.sup.-1 (hard glass of the borosilicate type) and 95.times.10.sup.-7 degrees K.sup.-1 (soft glass with lead oxide added). They are therefore not thermally matched to quartz with its extremely low value of maximally 5.times.10.sup.-7 degrees K.sup.-1. In other words, a glass solder or fused joint which could reliably seal the gas space of the laser cannot be made.